The invention relates to a process for determining the erosion caused by cavitation in components through which fluid flows.
In the case of pumps and other components through which fluid flows, cavitation occurs in the fluid conveyed under certain conditions. Thus, for example, at the inlet edges of the impeller vanes of a centrifugal pump zones having low pressure, which result in the formation of steam bubbles, occur as a result of local excess speeds when the local pressure drops below the steam pressure of the fluid conveyed. The steam bubbles are rinsed with the flow in high-pressure zones, where they implode. A very high pressure peak and a very high cavitation intensity occur locally may cause material erosion and cavitation damage.
The continuous assessment of the hydrodynamic cavitation intensity and the erosion rate caused by cavitation in components such as pumps, turbines, automatic control valves shut-off valves. And after is known. A known method is to measure the fluid-borne noise. An empirically determined connection between the fluid-borne noise and the erosion rate permits the quantitative assessment of the potential risk of cavitation damage.
A corresponding process with a device for determining the erosion rate is known, for example, from "Guideline for prevention of Cavitation in Centrifugal Feedpumps, EPRI GS-6398, Project 1884-10, Final Report, Electric Power Research Institute, Palo Alto, Cal., 1989", Pages 2-24 and also Page B-9.
The measurement of the fluid-borne noise depends on a corresponding pressure measuring device which is inserted into the component through which fluid flows. direct contact with the fluid. The provision of a corresponding aperture in the outer wall of the component through which fluid flows is extremely problematic for safety reasons may be, for example in the nuclear industry. For this reason the known process is unsuitable for short-term inspection of existing plant equipment. A further disadvantage of the known process lies in the fact that the pressure gauge has to be fastened precisely inside tile component through which fluid flows for reasons relating to flow technology, in order to avoid measurement errors caused by air bubbles being deposited.
The object of the present invention is therefore to determine the erosion rate caused by cavitation without the necessity for a measuring sensor inside the component through which fluid flows.